1. Field of the Invention
The present invention relates generally to synchronization, more specifically to synchronization of laser systems, and most specifically to synchronization of laser systems with femtosecond synchronization levels.
2. Related Art
Previous methods of synchronization of pulsed lasers have employed transmission of short pulses, or high frequency RF signals, or single optical frequencies. These methods have demonstrated low timing jitter between lasers, but have relative disadvantages. Transmitting short pulses for timing requires the pulses remain short in duration while being transmitted over long distances in fiber. Such transmission tends to broaden the pulses and distort temporal information. Synchronization using high RF frequencies requires transmission over electrical cable or fiber. Stabilization of the temporal delay in electrical cable is limited by phase detection of the RF signal to hundreds of femtoseconds, while transmission of RF over fiber requires optical-to-electrical conversion, which is unstable and susceptible to noise. Transmission using single optical frequencies requires that the lasers to be synchronized are stabilized with respect to the frequency offset between the carrier and the pulse envelope. This may not be possible for many lasers that need to be synchronized to the sub-10 fs regime.